/*******************************************************************************
 * Copyright (c) 2000, 2010 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.ceylon.ide.eclipse.code.browser;

import java.io.IOException;
import java.io.StringReader;
import java.util.Iterator;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.ListenerList;
import org.eclipse.jface.action.ToolBarManager;
import org.eclipse.jface.resource.JFaceResources;
import org.eclipse.jface.text.IDelayedInputChangeProvider;
import org.eclipse.jface.text.IInformationControlExtension2;
import org.eclipse.jface.text.IInputChangedListener;
import org.eclipse.jface.text.TextPresentation;
import org.eclipse.swt.SWT;
import org.eclipse.swt.SWTError;
import org.eclipse.swt.browser.Browser;
import org.eclipse.swt.browser.LocationListener;
import org.eclipse.swt.browser.ProgressAdapter;
import org.eclipse.swt.browser.ProgressEvent;
import org.eclipse.swt.custom.StyleRange;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.Font;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.graphics.TextLayout;
import org.eclipse.swt.graphics.TextStyle;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Slider;

import org.eclipse.ceylon.ide.eclipse.code.hover.AbstractInformationControl;
import org.eclipse.ceylon.ide.eclipse.code.html.HTML2TextReader;
import org.eclipse.ceylon.ide.eclipse.code.html.HTMLPrinter;
import org.eclipse.ceylon.ide.eclipse.util.DocBrowser;


/**
 * Displays HTML information in a {@link org.eclipse.swt.browser.Browser} widget.
 * <p>
 * This {@link IInformationControlExtension2} expects {@link #setInput(Object)} to be called with an
 * argument of type {@link BrowserInput}.
 * </p>
 * <p>
 * Moved into this package from <code>org.eclipse.jface.internal.text.revisions</code>.
 * </p>
 * <p>
 * This class may be instantiated; it is not intended to be subclassed.
 * </p>
 * <p>
 * Current problems:
 * <ul>
 * <li>the size computation is too small</li>
 * <li>focusLost event is not sent - see https://bugs.eclipse.org/bugs/show_bug.cgi?id=84532</li>
 * </ul>
 * </p>
 * 
 * @since 3.2
 */
public class BrowserInformationControl extends AbstractInformationControl 
        implements IInformationControlExtension2, IDelayedInputChangeProvider {
    
    /**
     * Tells whether the SWT Browser widget and hence this information
     * control is available.
     * 
     * @param parent the parent component used for checking or <code>null</code> if none
     * @return <code>true</code> if this control is available
     */
    public static boolean isAvailable(Composite parent) {
        if (!fgAvailabilityChecked) {
            try {
                Browser browser= new Browser(parent, SWT.NONE);
                browser.dispose();
                fgIsAvailable= true;

                Slider sliderV= new Slider(parent, SWT.VERTICAL);
                Slider sliderH= new Slider(parent, SWT.HORIZONTAL);
                int width= sliderV.computeSize(SWT.DEFAULT, SWT.DEFAULT).x;
                int height= sliderH.computeSize(SWT.DEFAULT, SWT.DEFAULT).y;
                fgScrollBarSize= new Point(width, height);
                sliderV.dispose();
                sliderH.dispose();
            } catch (SWTError er) {
                fgIsAvailable= false;
            } finally {
                fgAvailabilityChecked= true;
            }
        }

        return fgIsAvailable;
    }


    /**
     * Minimal size constraints.
     * @since 3.2
     */
    private static final int MIN_WIDTH= 80;

    private static final int MIN_HEIGHT= 50;


    /**
     * Availability checking cache.
     */
    private static boolean fgIsAvailable= false;

    private static boolean fgAvailabilityChecked= false;

    /**
     * Cached scroll bar width and height
     * @since 3.4
     */
    private static Point fgScrollBarSize;

    /** The control's browser widget */
    private DocBrowser fBrowser;

    /** Tells whether the browser has content */
    private boolean fBrowserHasContent;

    /** Text layout used to approximate size of content when rendered in browser */
    private TextLayout fTextLayout;

    /** Bold text style */
    private TextStyle fBoldStyle;

    private BrowserInput fInput;

    /**
     * <code>true</code> iff the browser has completed loading of the last
     * input set via {@link #setInformation(String)}.
     * @since 3.4
     */
    private boolean fCompleted= false;

    /**
     * The listener to be notified when a delayed location changing event happened.
     * @since 3.4
     */
    private IInputChangedListener fDelayedInputChangeListener;

    /**
     * The listeners to be notified when the input changed.
     * @since 3.4
     */
    private ListenerList<IInputChangedListener> fInputChangeListeners= 
            new ListenerList<IInputChangedListener>(ListenerList.IDENTITY);

    /**
     * The symbolic name of the font used for size computations, or <code>null</code> to use dialog font.
     * @since 3.4
     */
    private final String fSymbolicFontName;


    /**
     * Creates a browser information control with the given shell as parent.
     * 
     * @param parent the parent shell
     * @param symbolicFontName the symbolic name of the font used for size computations
     * @param resizable <code>true</code> if the control should be resizable
     * @since 3.4
     */
    public BrowserInformationControl(Shell parent, String symbolicFontName, 
            boolean resizable) {
        super(parent, resizable);
        fSymbolicFontName= symbolicFontName;
        create();
    }

    /**
     * Creates a browser information control with the given shell as parent.
     * 
     * @param parent the parent shell
     * @param symbolicFontName the symbolic name of the font used for size computations
     * @param statusFieldText the text to be used in the optional status field
     *            or <code>null</code> if the status field should be hidden
     * @since 3.4
     */
    public BrowserInformationControl(Shell parent, String symbolicFontName, 
            String statusFieldText) {
        super(parent, statusFieldText);
        fSymbolicFontName= symbolicFontName;
        create();
    }

    /**
     * Creates a browser information control with the given shell as parent.
     * 
     * @param parent the parent shell
     * @param symbolicFontName the symbolic name of the font used for size computations
     * @param toolBarManager the manager or <code>null</code> if toolbar is not desired
     * @since 3.4
     */
    public BrowserInformationControl(Shell parent, String symbolicFontName, 
            ToolBarManager toolBarManager) {
        super(parent, toolBarManager);
        fSymbolicFontName= symbolicFontName;
        create();
    }

    @Override
    protected void createContent(Composite parent) {
        fBrowser= new DocBrowser(parent, SWT.NONE);

        fBrowser.setProgressListener(new ProgressAdapter() {
            @Override
            public void completed(ProgressEvent event) {
                fCompleted= true;
            }
        });

        // Replace browser's built-in context menu with none
        fBrowser.setMenu(new Menu(getShell(), SWT.NONE));

        createTextLayout();
    }

    /**
     * {@inheritDoc}
     * @deprecated use {@link #setInput(Object)}
     */
    @Override
    public void setInformation(final String content) {
        setInput(new BrowserInput(null) {
            @Override
            public String getHtml() {
                return content;
            }
            @Override
            public String getInputName() {
                return "";
            }
        });
    }

    /**
     * {@inheritDoc} This control can handle {@link String} and
     * {@link BrowserInput}.
     */
    @Override
    public void setInput(Object input) {
        Assert.isLegal(input == null || 
                input instanceof String || 
                input instanceof BrowserInput);

        if (input instanceof String) {
            setInformation((String)input);
            return;
        }

        fInput= (BrowserInput) input;

        String content= null;
        if (fInput != null)
            content= fInput.getHtml();

        fBrowserHasContent= content != null && content.length() > 0;

        if (!fBrowserHasContent)
            content= "<html><body ></html>"; //$NON-NLS-1$

        boolean RTL= (getShell().getStyle() & SWT.RIGHT_TO_LEFT) != 0;
        boolean resizable= isResizable();

        // The default "overflow:auto" would not result in a predictable width for the client area
        // and the re-wrapping would cause visual noise
        String[] styles= null;
        if (RTL && resizable)
            styles= new String[] { "direction:rtl;", "overflow:scroll;", "word-wrap:break-word;" }; //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
        else if (RTL && !resizable)
            styles= new String[] { "direction:rtl;", "overflow:hidden;", "word-wrap:break-word;" }; //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
        else if (!resizable)
            //XXX: In IE, "word-wrap: break-word;" causes bogus wrapping even in non-broken words :-(see e.g. Javadoc of String).
            // Re-check whether we really still need this now that the Javadoc Hover header already sets this style.
            styles= new String[] { "overflow:hidden;"/*, "word-wrap: break-word;"*/}; //$NON-NLS-1$
        else
            styles= new String[] { "overflow:scroll;" }; //$NON-NLS-1$

        StringBuilder buffer= new StringBuilder(content);
        HTMLPrinter.insertStyles(buffer, styles);
        content= buffer.toString();

        /*
         * XXX: Should add some JavaScript here that shows something like
         * "(continued...)" or "..." at the end of the visible area when the page overflowed
         * with "overflow:hidden;".
         */

        fCompleted= false;
        fBrowser.setText(content);

        Object[] listeners= fInputChangeListeners.getListeners();
        for (int i= 0; i < listeners.length; i++)
            ((IInputChangedListener)listeners[i]).inputChanged(fInput);
    }

    @Override
    public void setVisible(boolean visible) {
        Shell shell= getShell();
        if (shell.isVisible() == visible)
            return;

        if (!visible) {
            super.setVisible(false);
            setInput(null);
            return;
        }

        /*
         * The Browser widget flickers when made visible while it is not completely loaded.
         * The fix is to delay the call to setVisible until either loading is completed
         * (see ProgressListener in constructor), or a timeout has been reached.
         */
        final Display display= shell.getDisplay();

        // Make sure the display wakes from sleep after timeout:
        display.timerExec(100, new Runnable() {
            @Override
            public void run() {
                fCompleted= true;
            }
        });

        while (!fCompleted) {
            // Drive the event loop to process the events required to load the browser widget's contents:
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }

        shell= getShell();
        if (shell == null || shell.isDisposed())
            return;

        /*
         * Avoids flickering when replacing hovers, especially on Vista in ON_CLICK mode.
         * Causes flickering on GTK. Carbon does not care.
         */
        if ("win32".equals(SWT.getPlatform())) //$NON-NLS-1$
            shell.moveAbove(null);

        super.setVisible(true);
    }

    @Override
    public void setSize(int width, int height) {
        fBrowser.setRedraw(false); // avoid flickering
        try {
            super.setSize(width, height);
        } finally {
            fBrowser.setRedraw(true);
        }
    }

    /**
     * Creates and initializes the text layout used
     * to compute the size hint.
     * 
     * @since 3.2
     */
    private void createTextLayout() {
        fTextLayout= new TextLayout(fBrowser.getDisplay());

        // Initialize fonts
        String symbolicFontName= fSymbolicFontName == null ? JFaceResources.DIALOG_FONT : fSymbolicFontName;
        Font font= JFaceResources.getFont(symbolicFontName);
        fTextLayout.setFont(font);
        fTextLayout.setWidth(-1);
        font= JFaceResources.getFontRegistry().getBold(symbolicFontName);
        fBoldStyle= new TextStyle(font, null, null);

        // Compute and set tab width
        fTextLayout.setText("    "); //$NON-NLS-1$
        int tabWidth= fTextLayout.getBounds().width;
        fTextLayout.setTabs(new int[] { tabWidth });
        fTextLayout.setText(""); //$NON-NLS-1$
    }

    @Override
    protected void handleDispose() {
        if (fTextLayout != null) {
            fTextLayout.dispose();
            fTextLayout= null;
        }
        fBrowser= null;

        super.handleDispose();
    }

    @Override
    public Point computeSizeHint() {
        Point sizeConstraints = getSizeConstraints();
        Rectangle trim = computeTrim();
        
        //FIXME: The HTML2TextReader does not render <p> like a browser.
        // Instead of inserting an empty line, it just adds a single line break.
        // Furthermore, the indentation of <dl><dd> elements is too small (e.g with a long @see line)
        TextPresentation presentation= new TextPresentation();
        HTML2TextReader reader= new HTML2TextReader(new StringReader(fInput.getHtml()), presentation);
        String text;
        try {
            text= reader.getString();
        } catch (IOException e) {
            text= "";
        }
        finally {
            try {
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        fTextLayout.setText(text);
        fTextLayout.setWidth(sizeConstraints==null ? SWT.DEFAULT : sizeConstraints.x-trim.width);
        Iterator<StyleRange> iter = presentation.getAllStyleRangeIterator();
        while (iter.hasNext()) {
            StyleRange sr = iter.next();
            if (sr.fontStyle == SWT.BOLD)
                fTextLayout.setStyle(fBoldStyle, sr.start, sr.start + sr.length);
        }

        Rectangle bounds = fTextLayout.getBounds(); // does not return minimum width, see https://bugs.eclipse.org/bugs/show_bug.cgi?id=217446
        int lineCount = fTextLayout.getLineCount();
        int textWidth = 0;
        for (int i=0; i<lineCount; i++) {
            Rectangle rect = fTextLayout.getLineBounds(i);
            int lineWidth = rect.x + rect.width;
            if (i==0) {
                lineWidth *= 1.25; //to accommodate it is not only bold but also monospace
                lineWidth += 20;
            }
            textWidth = Math.max(textWidth, lineWidth);
        }
        bounds.width = textWidth;
        fTextLayout.setText("");

        int minWidth = textWidth;
        int minHeight = trim.height + bounds.height;

        // Add some air to accommodate for different browser renderings
        minWidth += 30;
        minHeight += 60;

        // Apply max size constraints
        if (sizeConstraints!=null) {
            if (sizeConstraints.x!=SWT.DEFAULT)
                minWidth = Math.min(sizeConstraints.x, minWidth + trim.width);
            if (sizeConstraints.y!=SWT.DEFAULT)
                minHeight = Math.min(sizeConstraints.y, minHeight);
        }

        // Ensure minimal size
        int width = Math.max(MIN_WIDTH, minWidth);
        int height = Math.max(MIN_HEIGHT, minHeight);

        return new Point(width, height);
    }

    @Override
    public Rectangle computeTrim() {
        Rectangle trim= super.computeTrim();
        if (isResizable() && fgScrollBarSize!=null) {
            boolean RTL= (getShell().getStyle() & SWT.RIGHT_TO_LEFT) != 0;
            if (RTL) {
                trim.x-= fgScrollBarSize.x;
            }
            trim.width+= fgScrollBarSize.x;
            trim.height+= fgScrollBarSize.y;
        }
        return trim;
    }

    /**
     * Adds the listener to the collection of listeners who will be
     * notified when the current location has changed or is about to change.
     * 
     * @param listener the location listener
     * @since 3.4
     */
    public void addLocationListener(LocationListener listener) {
        fBrowser.addLocationListener(listener);
    }

    @Override
    public void setForegroundColor(Color foreground) {
        super.setForegroundColor(foreground);
        fBrowser.setForeground(foreground);
    }

    @Override
    public void setBackgroundColor(Color background) {
        super.setBackgroundColor(background);
        fBrowser.setBackground(background);
    }

    @Override
    public boolean hasContents() {
        return fBrowserHasContent;
    }

    /**
     * Adds a listener for input changes to this input change provider.
     * Has no effect if an identical listener is already registered.
     * 
     * @param inputChangeListener the listener to add
     * @since 3.4
     */
    public void addInputChangeListener(IInputChangedListener inputChangeListener) {
        Assert.isNotNull(inputChangeListener);
        fInputChangeListeners.add(inputChangeListener);
    }

    /**
     * Removes the given input change listener from this input change provider.
     * Has no effect if an identical listener is not registered.
     * 
     * @param inputChangeListener the listener to remove
     * @since 3.4
     */
    public void removeInputChangeListener(IInputChangedListener inputChangeListener) {
        fInputChangeListeners.remove(inputChangeListener);
    }

    @Override
    public void setDelayedInputChangeListener(IInputChangedListener inputChangeListener) {
        fDelayedInputChangeListener= inputChangeListener;
    }

    /**
     * Tells whether a delayed input change listener is registered.
     * 
     * @return <code>true</code> iff a delayed input change
     *         listener is currently registered
     * @since 3.4
     */
    public boolean hasDelayedInputChangeListener() {
        return fDelayedInputChangeListener != null;
    }

    /**
     * Notifies listeners of a delayed input change.
     * 
     * @param newInput the new input, or <code>null</code> to request cancellation
     * @since 3.4
     */
    public void notifyDelayedInputChange(Object newInput) {
        if (fDelayedInputChangeListener != null)
            fDelayedInputChangeListener.inputChanged(newInput);
    }

    @Override
    public String toString() {
        String style= (getShell().getStyle() & SWT.RESIZE) == 0 ? "fixed" : "resizeable"; //$NON-NLS-1$ //$NON-NLS-2$
        return super.toString() + " -  style: " + style; //$NON-NLS-1$
    }

    /**
     * @return the current browser input or <code>null</code>
     */
    public BrowserInput getInput() {
        return fInput;
    }

    @Override
    public Point computeSizeConstraints(int widthInChars, int heightInChars) {
        if (fSymbolicFontName == null)
            return null;

        GC gc= new GC(fBrowser.getDrawable());
        Font font= fSymbolicFontName == null ? JFaceResources.getDialogFont() : JFaceResources.getFont(fSymbolicFontName);
        gc.setFont(font);
        int width= gc.getFontMetrics().getAverageCharWidth();
        int height= gc.getFontMetrics().getHeight();
        gc.dispose();

        return new Point(widthInChars * width, heightInChars * height);
    }

}
